Vehicle speed monitoring systems

ABSTRACT

A system is disclosed for monitoring speed of highway vehicles from a central control station. The system includes posting devices positioned at intervals along the highway and adapted to receive a speed message from the control station and transmit the speed message to passing vehicles in a limited region of the highway in the form of an r-f signal. Each vehicle contains an rf receiver which is connected to the vehicle speedometer or other vehicle indication means in a manner that will provide, upon the occurrence of some predetermined excessive speed, an indication to the driver of the vehicle that the speed limit at that particular region of the highway is being exceeded. There is provision, also, for means for reporting back to the control station the occurrence of excessive vehicular speed as well as for providing accident warnings and the like.

United States Patent Angeloni s4] VEHICLE SPEED MONITORING [52] U.S. Cl...340/33, 325/117, 179/1 VE [51] Int. Cl. 608g 1/00 [58] Field oISearch..340/32, 33, 34; 325/1, I17;

179/4] A, I VE 11 1 3,680,043 51 July 25,1972

Primary Examiner--William C. Cooper Attorney-Robert Shaw [57] ABSTRACT Asystem is disclosed for monitoring speed of highway vehicles from acentral control station. The system includes posting devices positionedat intervals along the highway and adapted to receive a speed messagefrom the control station and transmit the speed message to passingvehicles in a limited region of the highway'in the form of an r-fsignal. Each vehicle contains an r-f receiver which is connected to thevehicle speedometer or other vehicle indication means in a manner thatwill pro- [56] v Rdmnm Cmd vide, upon the occurrence of somepredetermined excessive UNITED STATES PATENTS speed, an indication t0the dliVCl' 0f the VChlClC that speed limit at that particular region ofthe highway is being ex- Halstead ceeded Thc g is provision also formeans for re orting ba k 3,550,076 12/1970 Ken! m-340/32 X to thecontrol station the occurrence of excessive vehicular 2,734,131 2/1956Magnuskl- X speed as well as for providing accident warnings and thelike. 2,640,979 6/1953 Carter ....340/32 X 2,656,002 10/1953 Keeton eta] ..l80/82.l v 20 China, 8 Drawing Figures CAMERA v 7 8 i T I 7 CENTRALH'GHWAY r vzmcuz TUNED RELAY l CONTROL 8538: RECEIVER cmcuns BANK T l I2 1 3 I 20 I2 l TO FURTHER I DEVICES OVER-SPEED VEHICLE TRANSMITTERSPEEDOMETER l m 68 -71 m TERNAL AUDIO I SIGNAL I g l VEHICLE I RECEIVERT PATENTEDmzs quiz 3.680.043 snznanr'z' FROM g T 26 T 7 RECEIVER g sYSETJSIGNAL SET SIGNAL INVERTER 6'84 TAPE Hmmsm'r'ranl eo a 50 Fig. 2 55I Inventor Paul Ange 0m Attorney VEHICLE SPEED MONITORING SYSTEMS Thepresent invention relates to apparatus for remote speed control ofhighway vehicles and particularly to apparatus whereby signalsindicative of allowable speed are transmitted to passing vehicles atspaced intervals along the highway.

Speed control of highway vehicles such as automobiles, trucks, etc., hasbecome a matter of great public concern particularly in recent timeswith the advent of higher powered vehicles and the dramatic increase inhighway travel. There has been, therefore, a major eflort directed toupdating the approach to controlling the speed of such vehicles,including the use 'of radar systems and the like. An object of thepresent invention is to provide a high speed control system whereby theposting of the speed limit at any particular region along a highway canbe efl'ected from some remote location, a radiofrequency or other signalrepresentative of the posted speed being transmitted to a limited regionof the highway to be received by vehicles passing through that limitedregion and interpreted by apparatus in the vehicles.

A further object is to provide an audible signal within the vehicle,which is energized upon the occurrence of excessive vehicular speed.

A still further object is to provide means for transmitting a messageback to said remote location from the vehicle, the nature of the messagebeing indicative, for example, of the occurrence of an excessivevehicular speed, an accident on the highway, or some other similar typeevent.

Still other and further objects are contained in the followingdescription and are particularly delineated in the appended claims.

By way of summary, the objects of the invention are attained in highwayspeed monitoring apparatus that includes a plurality of posting devicesfor disposition along the highway, each device comprising a transmitteradapted to transmit a signal to a limited region of the highway toprovide an indication of proper vehicle speed at said region. A receivermounted in each vehicle is connected to a speedometer or other vehicularspeed indicating means. The receiver functions to receive and interpretthe transmitted signal and is interconnected with the speedometer insuch a way that upon the occurrence of excessive speed by the vehicle,as represented by the signal from the posting device, a circuit iscompleted to a sound generating device, light or other mechanism withinthe vehicle thereby to alert the driver that he is exceeding the postedspeed limit.

The invention will now be explained with reference to the accompanyingdrawing in which:

FIG. 1 is a block diagram of a system embodying the present inventiveconcept;

FIG. 2 is a block diagram of a portion of the system of FIG.

FIG. 3 is a block diagram of a further portion of the system of FIG. 1;

FIG. 4 is a circuit diagram of a simplified multicontact speedometerthat may be used in the system shown in FIG. 1;

FIG. 5 shows in detail a number of the block circuits of FIG.

FIG. 6 is a side view of a multi-contact speedometer that might be usedin connection with operative apparatus;

FIG. 7 is a view taken upon the line 7-7 in FIG. 6, looking in thedirection of the arrows; and

FIG. 8 is a schematic representation showing a limited portion of ahighway and a plurality of posting devices disposed therealong.

The concept herein discussed is concerned with transmitting a remotelycontrolled speed limit signal from a stationary signal device to passingvehicles. In the preferred embodiment the signal is in the form of aradio frequency (r-f) signal which contains modulation that can beremoved by appropriate receiving means in the vehicles and interrelatedwith the vehicle speed to provide an indication to the operator of thevehicle of the occurrence of speed in excess of the posted limit. In thepreferred form of apparatus the various speed limits are assignedfrequencies of say 17 to 21 KHL,

representing speeds of, say, 30 to mph, and the frequencies are imposedas speed messages upon a carrier for transmittal. The highway vehiclesare each provided with a receiver adapted to receive and interpret thesignal, the receiver being electrically connected to a speedometer torelate proper speed with vehicle speed and to provide an indication tothe driver and/or some remote operator of the. existence of excessivespeed.

Turning now to the figures, a system for monitoring vehicles on ahighway is shown generally at I, in FIG. I. The system is adapted toallow an operator at some remote central control location 2 to controlr-f outputs from a plurality of highway posting devices 3 (one suchdevice only is shown in FIG. 1). The r-f output of each such device iscontrolled by the operator to provide an output signal containing amessage which is interpreted by apparatus in a passing vehicle travelingalong the highway in the vicinity of the device 3 to provide an indi-.

cation of proper vehicle speed at that particular region of the highway.The vehicle apparatus is at which is contained within the blockdesignated 4 in FIG. I; the block 4, for present purposes, is aschematic representation of a vehicle passing along the highway in thevicinity of the posting device 3.

Each posting device 3, as shown in FIG. 2, contains a transmitter 4'adapted to transmit an r-f signal to a limited region of the highway inthe immediate vicinity of the posting device. A receiver 6 ismounted ineach vehicle 4 to receive, amplify and demodulate the signal; the outputof the receiver 6 is connected to a plurality of tuned circuits 7, theoutput of each tuned circuit being connected to a relay of a relay bank8 as shown more particularly in FIGS. 3 and 5. In FIG. 3 a plurality ofsuch tuned circuitsis shown at 9, l0 and II respectively, connected tothe control coils or other control means of relaytype switches 15,16 and17. Each tuned circuit is tuned to a particular frequency to pass acontrol voltage along to the associated relay only on the occurrence ofsuch particular frequency. The particular tuned circuit which providesan output voltage to its associated relay is detennined by the output ofthe transmitter 4, and, more particularly, by the modulation message.Thus, the output of the transmitter 4' can be frequency modulated oramplitude modulated and the modulation message is separated from the r-fcarrier by the receiver 6, the modulation message being passed from thereceiver 6 to the tuned circuits 7, as mentioned. 1

The relay bank 8 functions in conjunction with a multiplecontactspeedometer 12 to provide an audio indication of excessive speed to thevehicle operator by actuating a buzzer or other sound means 18 containedwithin an internal audio. signal means- 13. The speedometer, except uponthe occurrence of excessive vehicle speed, functions similarly tospeedometers now used in motor vehicles. The foregoing function isillustrated schematically in FIG. 4 where the relay 15 only is shownconnected to electrical contacts designated 40 and 45 in the figure; thenumerals 40 and 45 (and also the numerals 50, 55, 60, 65 and 70)represent designation of the electrical contacts in the speedometer aswell as vehicle speed designations.

Assume the relay 15 is closed under the control of the signal from aparticular posting device 3, and assume further that the posted speed is35 mph. The relay 15 is connected, as shown, to the electrical contactpoint 40 so that at 40 mph an electric circuit is completed from groundG through the relay l5 and the speedometer 12 (the speedometer needle,designated 47, functions as a brush, as later explained) to a battery 19and thence the buzzer 18 to ground G. (Ground here designates a commonchassis connection rather than actual earthing.) At 45 mph a circuit iscompleted through the contact 45 to an over-speed transmitter 20 which,as hereinafter discussed, transmits a pre-recorded message to theposting device 3. The circuit in FIG. 4 is an over-simplification ofcircuitry which actually is used to perform the functions justdescribed. Thus, it

is not desirable that the electric circuit through the contact 45 makeand then break, but, rather, it is necessary that the circuit once madebe maintained. Also, it is desirable that the cirof shortmtime speedsthat exist during passing, forexample.

Thus, the circuit shown in block diagram form in FIG. 5, is used inoperable systems; some of the numerals shown in FIG. 5 duplicatenumerals previously used to designate similarly functioning apparatus.

The circuit shown in FIG. 5 includes a plurality of momentary relays 25,25', etc. (for simplicity only two such relays and associated elementsare shown, but in operable apparatus several more such relays would beused and would operate in the manner hereinafter outlined in connectionwith relays 25 and 25') connected to receive what is termed a set signalfrom associated tuned circuits 26, 26', etc., respectively, the setsignal being connected to energize the coils 24 and 24', etc. of therespective relays. Each of the momentary relays is connected to furtherrelays to make up a relay set. The explanation to follow is, in themain, concerned with the relay 25 and associated elements since all therelay sets function similarly.

The output of the vehicle receiver 6 is at the 17 KHz. to 21 KHz.modulation frequencies before mentioned; the output is connected to thetuned circuits 7, shown in FIG. 5 to be the tuned circuits 26, 26, etc.If the modulation is at the resonant frequency of the tuned circuit 26 avoltage will appear as a pulse across the coil 24 of the relay 25. Therelay 25 is normally open and upon receiving the voltage pulse itscontacts close momentarily. The contacts of the relay 25 are seriallyconnected with the coil of a latching relay 28, the complete circuitbeing from ground through a battery 49 to an inverter 51 (12 volts dc tol volts ac in operable apparatus), the out put of the inverter beingconnected through the relay and the coil of the relay 28 and back toground. The relay 28 is normally open and when closed, upon energizationof its coil, it remains closed until opened by a relay 29 in a mannerhereinafter discussed. The contacts of the relay28 are connected inseries with a switch 40' in the speedometer 12 by a conductor 33 andthen to ground. When the contacts of the relay 28 are closed a circuitis completed from ground through .thebattery 49, through the coil of arelay 31, through the relay 28' andthespeedometer switch 40', whenclosed, to ground. In

this fashion the vehicle apparatus is set" to provide an indication ofexcess speed above the 35 mph speed limit previously discussed; in the.disclosed example the indication is activation of the buzzer l8.

As shown 'in FIGS. 6 and 7, the function of the switches shown at 40',and in FIG. 5 can be performed by a multi-contact speedometer havingstationary commutator 41 and a revolvable member 42 adapted to revolveupon bearings 44 and 46 to various angles from some zero point as afunction of vehicle speed. The brush 47 and wiper 47 serve to complete acircuitto the particular commutator segment 40, 45, 50, etc. It will benoted that electrical contact between the brush 47 and, say, the segment40 will continue, once made, for some period of time since each segmentspans about four mph (the intermediate insulation spans about one mph).From the foregoing explanation, it can be seen that in order for therelay 31 to close two events must occur: one, the relay 28 must beclosed by a signal from the receiver 6 and, two, the speedometer 12 mustbe in a position to provide contact between the brush 47 and the contactelement 40 (i.e., the switch 40' in FIG. 5 must be closed). The relay31, when closed, is connected to energize a buzzer or other sounddevice, as before mentioned, the circuit being from the battery 49through the relay 3] to the buzzer 18.

The relay 29 is mechanically interconnected with the relay 28, asrepresented by the dotted line labeled 61, to open and close with therelay 28, and it is a normally open, momentary type relay which, intheabsence of the mechanical interconnection, would not close but whenclosed it opens upon the occurrence of a voltage across its coil shownat 21 in FIG. 5. The voltage to the coil 21 is furnished by the inverter51 through a relay 27 which acts to reset to open the latching relay 28and further similarly functioning relays 62, etc.

Resetting is accomplished in each instance by applying a voltage to thecoil of the associated mechanically interconnected relay such as, forexample, the relay 29 in the case of the relay 28 and a momentary relay63 in the case of the relay 62. The coils of the relays 29, 63, etc. areso wound that, when energized, each opens the contacts of the respectiverelays 29, 63, etc., and thereby opens the contacts of the relays 28,62, etc. respectively interconnected therewith. The relay 27 is also anormally open momentary relay and its contacts are closed upon receiptof a reset voltage by its coil from the vehicle receiver labeled 6' inFIG. 1. The reset signal originates at a posting device 3' whichcontains a transmitter which transmits a continuous r-f signal to alimited region of the highway. When an automobile passes the device 3',all the relays 28, 62,

etc. are reset to open. The receiver 6 (as does also, the receiver6).includes input means to receive the r-f carrier, amplifier circuitry,and mixing circuitry to remove a modulation signal from the carrier, andit is the modulation signal that is connected to the coil of the relay27. The posting devices 3', as shown in FIG. 8, are disposed between theposting devices 3 along the highway, thereby to reset the automobilecircuitry just prior to passing a subsequent device 3 for receipt of afurther speed signal (which may difler from the speed signal of the lastdevice 3). The rest posting devices 3' may also be placed at entranceramps of limited access highways.

In the explanation in the previous paragraphs the speed limit was takento be 35 mph and the buzzer 18, as explained, is caused to emit soundwhen the vehicle speed reaches 40 mph, at which time the switch 40'closes. At 45 mph the switch 40' opens and a switch 45 closes therebycompleting an electric circuit from the battery 49 through the coil of anormally open relay 37, the relay 29, and the switch 45' to ground. Therelay 37, when closed, completes a circuit to a further buzzer 64. Therelay 37 is a momentary relay but it remains closed so long as theswitch 45 and therelay 29 are closed. If the vehicle speed increasesmuch above 45 mph, the

switch 45' opens which, in the absence of some altemate'arrangement,would result in theopening of the circuit to the buzzer 64. To preventthat possibility, a'latching relay 66 is provided and connected to closewhen the relay 37 closes so that even when the relay 37 opens a completecircuit exists from the battery 49 through the relay 66 tothe buzzer 64.

Only by reducing the vehicle speed down to'40 mph can the buzzer 64 bedisconnected. When that is done, the'relay 31 is closed, as before, anda circuit is completed through the relay- 31 to the coil labeled 67' ofa relay 67; the coil 67' is wound so that, when energized, it opens thecontacts of the relay 67, and, thus, the relay 66 to which it ismechanically interconnected, as shown. When the relays 66 and 67 are inthe closed condition, they serve also to complete circuits to a tapedevice 68 and the transmitter 20. The tape plays some pre-recordedmessage, such as the vehicle registration number, repetitiously, and thetransmitter 20, if the circuit remains closed 10 to 15 seconds,transmits the message to the nearest posting device 3 for transmittal tothe central control 2. The particular posting device receiving andre-transmitting the message is, of course, known at the central control2. The tape 68 and transmitter 20 cease to function when the relays and67 are opened in the manner before discussed. The delay is furnished bya delay means 71.

The switch shown at 72 in FIG. 5 is manually operated and provides meansby which the relay 66 can be closed irrespec-.

tive of messages from other parts of the circuit and can be used toindicate occurrence of an accident, breakdown or'the like. The postingdevices 3 can include lighted speed signs, warning lights and the like,all of which can be controlled from the central control 2, and incentral control the position of the various posting devices can be shownon a highway map by the rence of an excess speed of, say, 45 mph forsome predetermined length of time a pre-recorded message on a magnetictape or the like, is transmitted by the transmitter 20. The tapedmessage can contain the registration number of the violating vehicle,for example. By using appropriate switching and taped message, thetransmitter 20 can function to report accidents along the highway, aswell, as before discussed. The transmitted message from the transmitter20 is received by a receiver 21' and re-transmitted to the centralcontrol station 2 by a transmitter 22. A television camera 23 can bemounted upon the posting device 3 to provide visual monitoring of thehighway in the vicinity of the device and signals from the camera can betransmitted by microwave, line-of-sight transmission or coaxial cable,as desired.

The speed signals from the central control 2 to the posting device 3 canbe carried over telephone lines. Posting a particular speed can beaccomplished by closing a push-button or other switch at the centralcontrol station to energize a par- .ticular oscillator in the postingdevice thereby to provide, for example, a predetermined frequency outputfrom the device; or speed indication signals can be provided byamplitude or frequency modulating a carrier.

The relay used may be conventional relay switches or semiconductorswitches or reed switches, and integrated circuitry may be used toprovide compact packaging of large portions of the apparatus hereindescribed. These and further modifications will occur topersons skilledin the art.

What is claimed is:

l. A system for remotely establishing speed limits for vehicles on ahighway and for monitoring the speed of the vehicles that comprises, incombination, a plurality of posting devices disposed along the highway,each device including a transmitter adapted to transmit aradio frequencysignal to a limited region of the highway, the signal being modulated toprovide an indication of proper speed at said region, a receiver mountedin each vehicle to receive and demodulate said signal, the output of thereceiver being connected to a plurality of tuned circuits, switch meansconnected to receive the output of each tuned circuit and to becontrolled by a voltage from the associated tuned circuit, theparticular tuned circuit which provides an output voltage beingdetermined by the output frequency of the demodulated receiver output, aspeedometer having electric contact points at various speed positionsand pickup means adapted to make electrical contact with the contactpoints upon the occurrence of a particular speed and complete anelectric circuit thereby through the switches and means for conveying amodulation signal from a central control station to the posting devicesto establish the speed limit at each region posting the highway.

2. A system as claimed in claim 1 in which the transmitter is frequencymodulated to provide an output frequency that is indicative of properspeed of vehicle operation.

3. A system as claimed in claim 1 in which the transmitter is amplitudemodulated to provide an output signal that comprises a modulatedcarrier, the modulations providing the means by which proper speedsignals are transmitted to the vehicle.

4. A system as claimed in claim 1 which includes a warning deviceconnected in said electric circuit to be actuated upon occurrence ofsaid particular speed.

5. A system as claimed in claim 4 in which the warning device includes abuzzer and the like to provide the driver of the vehicle with anindication of excess vehicle speed.

6. A system as claimed in claim Sand including apparatus adapted to playa recorded message and a further transmitter to transmit the message,delay means being provided in said apparatus to provide a message onlyat such times as the vehicle exceeds proper speed by a predeterminedamount for a predetermined time period.

7. A system as claimed in claim 6 in which the posting device contains areceiver tuned to receive the message transmitted from the vehicle and astill further transmitter to retransmit the message to the centralcontrol station.

prises, in combination, a plurality of posting devices disposed alongthe highway, each device including a transmitter adapted to transmit asignal toa limited region of the highway, the signal being modulated toprovide a message indicative of proper vehicle speed at said region, areceiver mounted in each vehicle to receive said signal and provide anoutput, speed detecting means having means at various vehicle speeds .tocomplete an electric circuit upon occurrence of the particular speed,the receiver and the speed detecting means being so interconnected thatthe 'speed in which the circuit is completed is determined by the outputof the receiver, and means for conveying said message from a controlstation to the posting devices to establish the speed limit at eachregion of the highway.

11. A system as claimed in claim 10 in which the signal is at radiofrequency and the receiver demodulates the signal to provide an outputwhich isconnected to a plurality of tuned circuits.

12. A system as claimed in claim 11 in which the speed detecting meansis a multiple-electric-contact speedometer and in which a relay bank isconnected between the tuned circuit and the contacts of the speedometer,one relay of said bank being serially connected with each contact of thespeedometer to complete a circuit through said one relay to theassociated speedometer contact in response to a voltage from the tunedcircuit associated with said one relay.

13. A system as claimed in claim 12 in which the relay bank comprises aplurality of relay sets, each such set being connected to receive theoutput of a particular tuned circuit, and each set comprising: amomentary relay the holding coil of which is connected to receive thetuned circuit output, a latching relay the holding coil of which isconnected in series with the momentary relay, and a further momentaryrelay mechanically interconnected to reset the latching relay, thelatching relay of each set being serially connected to one speedometercontact and the further momentary relay being serially connected toanother speedometer contact to complete a circuit through each of therelays to the associated speedometer contact in response to a voltagefrom said particular tuned circuit.

14. A system as claimed in claim 13 in which the speedometer comprises abrush adapted to move from contact to contact in response to changes invehicle speed and thereby complete a circuit through the particularcontact to the brush upon occurrence of that particular speed.

15. Apparatus of claim 14 and including audio means connected to beactuated when the circuit is closed through the brush thereby toindicate the existence of excessive speed.

16. A system as claimed in 13 in which further posting devices aredisposed along the highway, each such further device having atransmitter, and a further receiver mounted in each vehicle to receivethe output of the further transmitter and connected to provide a resetvoltage to said further momentary relay.

[7. A system as claimed in claim 16 in which the further receiverprovides an output to a momentary reset relay the contacts of which areserially connected with the coils of each said further momentary relaythereby, upon receipt of a reset signal, to activate each of the furthermomentary relay to reset each of the latching relays.

18. A system for remotely establishing speed limits for vehicles on ahighway and for monitoring said vehicles that comprises, in combination,a plurality of posting devices disposed along the highway, each deviceincluding a transmitter adapted to transmit a signal to a limited regionof the highway to provide an indication of proper vehicle speed at saidregion, means to control the transmitter from a remote location toimpose a message upon the transmitted signal indicative of 19. A systemas claimed in claim 18 that includes means in the vehicle operable toplay a recorded message and a further transmitter to transmit themessage and in which each posting device contains a receiver tuned toreceive the message trans-.

mitted from the vehicle and a still further transmitter to retransmitthe message to said remote location. I

20. A system as claimed in claim 19 that includes switch meansassociated with each said further transmitter to initiate the playing ofa recorded message for transmittal to the remote location.

1. A system for remotely establishing speed limits for vehicles on ahighway and for monitoring the speed of the vehicles that comprises, incombination, a plurality of posting devices disposed along the highway,each device including a transmitter adapted to transmit a radiofrequency signal to a limited region of the highway, the signal beingmodulated to provide an indication of proper speed at said region, areceiver mounted in each vehicle to receive and demodulate said signal,the output of the receiver being connected to a plurality of tunedcircuits, switch means connected to receive the output of each tunedcircuit and to be controlled by a voltage from the associated tunedcircuit, the particular tuned circuit which provides an output voltagebeing determined by the output frequency of the demodulated receiveroutput, a speedometer having electric contact points at various speedpositions and pickup means adapted to make electrical contact with thecontact points upon the occurrence of a particular speed and complete anelectric circuit thereby through the switches and means for conveying amodulation signal from a central control station to the posting devicesto establish the speed limit at each region posting the highway.
 2. Asystem as claimed in claim 1 in which the transmitter is frequencymodulated to provide an output frequency that is indicative of properspeed of vehicle operation.
 3. A system as claimed in claim 1 in whichthe transmitter is amplitude modulated to provide an output signal thatcomprises a modulated carrier, the modulations providing the means bywhich proper speed signals are transmitted to the vehicle.
 4. A systemas claimed in claim 1 which includes a warning device connected in saidelectric circuit to be actuated upon occurrence of said particularspeed.
 5. A system as claimed in claim 4 in which the warning deviceincludes a buzzer and the like to provide the driver of the vehicle withan indication of excess vehicle speed.
 6. A system as claimed in claim 5and including apparatus adapted to play a recorded message and a furthertransmitter to transmit the message, delay means being provided in saidapparatus to provide a message only at such times as the vehicle exceedsproper speed by a predetermined amount for a predetermined time period.7. A system as claimed in claim 6 in which the posting device contains areceiver tuned to receive the message transmitted from the vehicle and astill further transmitter to re-transmit the message to the centralcontrol station.
 8. A system as claimed in claim 7 including manualswitch means associated with each further transmitter for producing asignal of a predetermined nature to the further transmitter fortransmittal to said central control station.
 9. A system as claimed inclaim 1 including a control circuit connected between said postingdevice and the central control station, the modulation of the signaltransmitted from each posting device being effected from said centralcontrol station.
 10. A system for remotely establishing speed limits forvehicles on a highway and for monitoring said vehicles that comprises,in combination, a plurality of posting devices disposed along thehighway, each device including a transmitter adapted to transmit asignal to a limited region of the highway, the signal being modulated toprovide a message indicative of proper vehicle speed at said region, areceiver mounted in each vehicle to receive said signal and provide anoutput, speed detecting means having means at various vehicle speeds tocomplete an electric circuit upon occurrence of the particular speed,the receiver and the speed detecting means being so inteRconnected thatthe speed in which the circuit is completed is determined by the outputof the receiver, and means for conveying said message from a controlstation to the posting devices to establish the speed limit at eachregion of the highway.
 11. A system as claimed in claim 10 in which thesignal is at radio frequency and the receiver demodulates the signal toprovide an output which is connected to a plurality of tuned circuits.12. A system as claimed in claim 11 in which the speed detecting meansis a multiple-electric-contact speedometer and in which a relay bank isconnected between the tuned circuit and the contacts of the speedometer,one relay of said bank being serially connected with each contact of thespeedometer to complete a circuit through said one relay to theassociated speedometer contact in response to a voltage from the tunedcircuit associated with said one relay.
 13. A system as claimed in claim12 in which the relay bank comprises a plurality of relay sets, eachsuch set being connected to receive the output of a particular tunedcircuit, and each set comprising: a momentary relay the holding coil ofwhich is connected to receive the tuned circuit output, a latching relaythe holding coil of which is connected in series with the momentaryrelay, and a further momentary relay mechanically interconnected toreset the latching relay, the latching relay of each set being seriallyconnected to one speedometer contact and the further momentary relaybeing serially connected to another speedometer contact to complete acircuit through each of the relays to the associated speedometer contactin response to a voltage from said particular tuned circuit.
 14. Asystem as claimed in claim 13 in which the speedometer comprises a brushadapted to move from contact to contact in response to changes invehicle speed and thereby complete a circuit through the particularcontact to the brush upon occurrence of that particular speed. 15.Apparatus of claim 14 and including audio means connected to be actuatedwhen the circuit is closed through the brush thereby to indicate theexistence of excessive speed.
 16. A system as claimed in 13 in whichfurther posting devices are disposed along the highway, each suchfurther device having a transmitter, and a further receiver mounted ineach vehicle to receive the output of the further transmitter andconnected to provide a reset voltage to said further momentary relay.17. A system as claimed in claim 16 in which the further receiverprovides an output to a momentary reset relay the contacts of which areserially connected with the coils of each said further momentary relaythereby, upon receipt of a reset signal, to activate each of the furthermomentary relay to reset each of the latching relays.
 18. A system forremotely establishing speed limits for vehicles on a highway and formonitoring said vehicles that comprises, in combination, a plurality ofposting devices disposed along the highway, each device including atransmitter adapted to transmit a signal to a limited region of thehighway to provide an indication of proper vehicle speed at said region,means to control the transmitter from a remote location to impose amessage upon the transmitted signal indicative of proper speed at saidregion, a receiver mounted in each vehicle to receive said signal andprovide an output, and speed detecting means mounted in each vehicle,the receiver and the speed detecting means being interconnected toprovide a indication of vehicle speed in excess of the proper vehiclespeed at said region.
 19. A system as claimed in claim 18 that includesmeans in the vehicle operable to play a recorded message and a furthertransmitter to transmit the message and in which each posting devicecontains a receiver tuned to receive the message transmitted from thevehicle and a still further transmitter to re-transmit the message tosaid remote location.
 20. A system as claimed in claim 19 that includesswitch means assocIated with each said further transmitter to initiatethe playing of a recorded message for transmittal to the remotelocation.